September 2015
Volume 56, Issue 10
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Genetics  |   September 2015
Association of ERAP1 Gene Polymorphisms With Behçet's Disease in Han Chinese
Author Affiliations & Notes
  • Lijun Zhang
    The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, People's Republic of China
  • Hongsong Yu
    The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, People's Republic of China
  • Minming Zheng
    The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, People's Republic of China
  • Hua Li
    The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, People's Republic of China
  • Yunjia Liu
    The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, People's Republic of China
  • Aize Kijlstra
    University Eye Clinic Maastricht, Maastricht, The Netherlands
  • Peizeng Yang
    The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, People's Republic of China
  • Correspondence: Peizeng Yang, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Ophthalmology and Chongqing Eye Institute, Chongqing, PR China, 400016; peizengycmu@126.com
Investigative Ophthalmology & Visual Science September 2015, Vol.56, 6029-6035. doi:10.1167/iovs.15-17544
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      Lijun Zhang, Hongsong Yu, Minming Zheng, Hua Li, Yunjia Liu, Aize Kijlstra, Peizeng Yang; Association of ERAP1 Gene Polymorphisms With Behçet's Disease in Han Chinese. Invest. Ophthalmol. Vis. Sci. 2015;56(10):6029-6035. doi: 10.1167/iovs.15-17544.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Behçet's disease (BD) is a common uveitis entity in China. The endoplasmic reticulum aminopeptidase 1 (ERAP1), has a significant influence on the stability and immunological properties of MHC-I loaded peptides. In the present study, we investigated the association of ERAP1 gene polymorphisms with BD in a Chinese Han population.

Methods: A two-stage case-control study was carried out in 930 BD patients and 1704 healthy controls. Seven single nucleotide polymorphisms (SNPs) of the ERAP1 gene were determined using a PCR restriction fragment length polymorphism (PCR-RFLP) assay and one SNP was genotyped by TaqMan SNP genotyping assay. Furthermore, ERAP1 expression in peripheral blood mononuclear cells (PBMCs) was examined in genotyped individuals by real-time PCR.

Results: The result demonstrated that the frequencies of the A allele of rs1065407 and C allele of rs10050860 were significantly decreased in BD patients (Pc = 8.5 × 10−8, OR = 0.51; Pc = 1.1 × 10−5, OR = 0.54, respectively). No significant association was observed for the other six SNPs. ERAP1 expression in AA carriers of rs1065407 and CC carriers of rs10050860 was higher than that observed in AC/CC carriers (P = 0.022) or CT/TT carriers (P = 0.018) by LPS-stimulated PBMCs, respectively. In addition, the expression of ERAP1 in active BD patients not receiving immunosuppression was significantly lower than that in healthy controls (P = 3.8 × 10−4).

Conclusions: Our study showed that rs1065407 and rs10050860 of the ERAP1 gene may contribute to the genetic susceptibility of BD by modulating the expression of ERAP1.

Behçet's disease (BD) is one of the multisystem autoimmune or autoinflammatory diseases of complex pathogenesis characterized by recurrent ulcerations of the oral cavity and genitalia, representative skin lesions, and severe ocular inflammation. It can also affect digestive, cardiovascular, and nervous systems.1,2 The pathogenic pathways of BD are largely unknown. Besides geographic tendency, numerous studies have indicated that the occurrence of BD is associated with genetic, immune, and environmental factors. Among all genetic factors, HLA-B51 has been proven as the strongest risk gene for BD, which was confirmed in various populations.3 However, other factors besides HLA-B51 are also involved in the inheritance of BD.46 
Endoplasmic reticulum amino peptidase1 (ERAP1), which is located at 5q15, has two major functions. First, it degrades intracellular precursors to small peptides that can subsequently attach to major histocompatibility complex (MHC) class I molecules forming the MHC-I-antigenic peptide complex.710 Second, ERAP1 is involved in cleaving cytokine receptors on the surface of cells, such as TNF receptor (TNFR1), IL-1 receptor-2 (IL-1R2), and IL-6 receptorα (IL-6Rα).1113 It may be involved in pathogenesis of BD either through its function to trim peptides before loading into HLA class I molecules, such as HLA-B51, or through its proposed role in shedding proinflammatory cytokine receptors from the cell wall. Recently, various groups have shown that polymorphisms of the ERAP1 gene are associated with autoimmune disease susceptibility in various populations.1429 For instance, genome-wide association studies (GWAS) have identified ERAP1 as a susceptibility gene for psoriasis in Chinese individuals14,15 and ankylosing spondylitis (AS) in Europeans.27,28 In addition, genetic surveys for multiple sclerosis from Italy16; Kawasaki disease in China29; and AS in China,1720 Spain,21 Turkey,22 Iran,23 Portugal,24 Korea,25 and Europe,26 have shown an association with ERAP1 polymorphisms. Moreover, a GWAS in a Turkish population found that two single nucleotide polymorphisms (SNPs) (rs10050860 and rs17482078) in ERAP1, which are in strong linkage disequilibrium (LD), were both associated with risk for BD with uveitis.30 The association of genetic variants of ERAP1 with the susceptibility of BD in a Chinese Han population has, however, not yet been reported and was therefore the subject of the study presented here. 
Materials and Methods
Subjects
For the case-control study, a total of 930 (first stage: 382, second stage: 548) unrelated Chinese Han patients with BD and 1704 (first stage: 570, second stage: 1134) Chinese Han healthy controls were recruited from the Zhongshan Ophthalmic Center of Sun Yat-sen University (Guangzhou, China) and the department of ophthalmology in the First Affiliated Hospital of Chongqing Medical University (Chongqing, PR China) from April 2007 to November 2014. All patients were diagnosed according to the international criteria for diagnosis of BD.31 The individuals studied in the first stage and second stage were randomly selected. This study was approved by the Ethical Committee of Chongqing Medical University and written informed consent was obtained from all subjects. 
Genotyping
Genomic DNA was isolated from peripheral blood cells of patients and healthy controls using the QIAamp DNA Blood Mini Kit (250) (QIAGEN, Valencia, CA, USA). The choice of SNPs of the ERAP1 gene was based on previously reported associations with susceptibility to other autoimmune diseases1429 and from the GWAS report for BD in Turkish patients.30 Linkage equilibrium (LD) and minor allele frequency (MAF) were analyzed by Haploview software 4.2 (Broad Institute, Cambridge, MA, USA). We eliminated one SNP (rs28366066) that was not polymorphic in the Chinese population and finally selected eight SNPs (the MAF at each locus was required to be >0.05 in Han Chinese in Beijing, with an r2-value of LD <0.8 between adjacent markers). Seven SNPs (rs27038, rs1065407, rs149481, rs10050860, rs27044, rs27980, and rs13167972) were genotyped using the PCR restriction fragment length polymorphism assay (PCR-RFLP) (specific restriction enzymes for each SNP are shown in Table 1). The rs7711564 polymorphism was genotyped by TaqMan SNP Genotyping Assay (TagMan assay ID: C_3056830_20). Moreover, the assay validity of genotyping was checked using direct sequencing in 3% of the samples (Sangon Biotech, ShangHai, China). The genotyping success rate for all the SNPs tested in our study ranged from 94.9% to 100%. 
Table 1
 
Primers and Restriction Enzymes Used for RFLP Analysis
Table 1
 
Primers and Restriction Enzymes Used for RFLP Analysis
Cell Isolation and Culture
Ficoll-Hypaque density-gradient centrifugation was used to obtain peripheral blood mononuclear cells (PBMCs) from venous blood samples. The PBMCs were counted by microscope and then seeded into 24-well culture plates (1 × 106 cells per well). The culture medium consisted of RPMI medium 1640, 10% fetal calf serum (Greiner, Wemmel, Belgium), 100 U/mL penicillin, and 100 μg/mL streptomycin. To investigate the effect of gene polymorphisms on the expression of ERAP1, PBMCs were cultured with 100 ng/mL lipopolysaccharide to simulate an inflammatory signal (LPS; Sigma-Aldrich Corp., St. Louis, MO, USA) and harvested at 24 hours.32 
Real-Time PCR
Total RNA was extracted from PBMCs using TRIzol Reagent (Invitrogen, San Diego, CA, USA). The purified RNA was reverse transcribed to single-stranded cDNA using the reverse transcription reagent kit (Takara Biotechnology Co., Ltd., Ostu, Japan) and then the expression of ERAP1 was measured by 7500 real-time instrument (ABI, Foster City, CA, USA). The following sequences of the sense and antisense primers of ERAP1 were used: forward 5′-ACAGATGGTGTAAAAGGGATGG-3′ and reverse 5′-GCAGTGTCCAAGTGTTCATCAT-3′. For the internal reference gene, β-actin was chosen and its expression was detected by the following primers: forward 5′-GGATGCAGAAGGAGATCACTG-3′ and reverse 5′-CGATCCACACGGAGTACTT-3′. Relative expression levels of ERAP1 were calculated using the 2−△△Ct method. 
Statistical Analysis
Genotype frequencies were estimated by direct counting. Allele and genotype frequencies in both cases and controls were tested for Hardy-Weinberg equilibrium (HWE) by the SHEsis method (available in the public domain at http://analysis.bio-x.cn/myAnalysis.php). The odds ratio (OR) and 95% confidence intervals (95% CIs) were calculated by SPSS 19.0 software (IBM SPSS Statistics, IBM Corporation, Chicago, IL, USA). The P values were corrected (Pc) for multiple comparisons with the Bonferroni correction method by multiplying with the number of analyses performed. The number of independent comparisons is 24. A Pc value less than 0.05 was considered statistically significant. The nonparametric Mann-Whitney test or t-test was used to compare ERAP1 expression among the genotype groups. Two-tailed P values less than 0.05 were considered to be statistically significant. Data were shown as mean ± SD. 
Results
Allele and Genotype Frequencies of Tested SNPs in Patients and Controls
Characteristics of the BD patients are shown in Table 2. Overall, genotype and distribution of allele frequencies in patients and controls for the two SNPs in ERAP1 are displayed in Table 3. The other six SNPs are shown as Supplementary Material. The genotype frequencies of all SNPs did not deviate from HWE equilibrium (both Fisher's P and Pearson's P > 0.05). The results of direct sequencing were consistent with the results of the PCR-RFLP method. 
Table 2
 
Clinical Characteristics, Sex, and Age of BD Patients With Uveitis
Table 2
 
Clinical Characteristics, Sex, and Age of BD Patients With Uveitis
Table 3
 
Association of Two SNPs of ERAP1 With BD
Table 3
 
Association of Two SNPs of ERAP1 With BD
Our results showed that there was a significant difference between patients with BD and healthy controls concerning the frequencies of both rs1065407 and rs10050860. As shown in Table 3, in the first-stage study, the frequency of the A allele and AA genotype of rs1065407 in BD patients was significantly lower than in healthy controls (Pc = 0.011, OR = 0.53; Pc = 0.023, OR = 0.53, respectively). In the second-stage study, we tested a different set of BD patients and controls and restricted the study to the two SNPs that showed a significant association in the first stage study. A similar result as found in the first stage was observed in the second-stage study (Pc = 1.150 × 10−4, OR = 0.51; Pc = 1.315 × 10−4, OR = 0.49, respectively). Stronger significance became apparent after combining the data from the two stages (Pc = 9.677 × 10−8, OR = 0.51; Pc = 2.714 × 10−7, OR = 0.50, respectively). The frequency of the rs1065407 AC genotype was significantly increased in BD patients compared with healthy controls only in the second stage (Pc = 2.981 × 10−4, OR = 1.99). The same increase in the AC genotype frequency was observed in the combination of the two stages (Pc = 2.429 × 10−6, OR = 1.92). In addition, decreased frequencies of the rs10050860 C allele and CC genotype were observed in BD patients as compared with normal controls in the first stage (Pc = 0.012, OR = 0.51; Pc = 0.018, OR = 0.50 respectively). The result was confirmed both in the second stage (Pc = 8.724 × 10−3, OR = 0.57; Pc = 0.016, OR = 0.57, respectively) and after combining the data (Pc = 1.059 × 10−5, OR = 0.54; Pc = 3.086×10−5, OR = 0.54, respectively). The frequency of the rs10050860 CT genotype was significantly higher in BD patients when compared with healthy controls in the first stage (Pc = 0.043, OR = 1.91), second stage (Pc = 0.040, OR = 1.69), and the combination (Pc = 1.823 × 10−4, OR = 1.78). The genotype and allele frequencies for the other six SNPs tested showed no significant difference between patients and controls in the first stage. Taking into account the finance saving, we did not perform a second-stage study on these SNPs. 
A stratified analysis of the main associations by sex was also performed in this study. The result showed that the genotype and allele frequencies for rs1065407 showed significant differences between patients and controls in both male (A allele: P = 7.644 × 10−6, OR = 0.54; AA genotype: P = 3.484 × 10−5, OR = 0.55) and female patients (A allele: P = 1.616 × 10−4, OR = 0.43; AA genotype: P = 8.590 × 10−5, OR = 0.39) (Table 4). However, the genotype and allele frequencies for rs10050860 showed more significant differences in male (C allele: P = 1.012 × 10−5, OR = 0.52; CC genotype: P = 7.617 × 10−5, OR = 0.52) compared with that in female patients (C allele: P = 0.030, OR = 0.58; CC genotype P = 0.040, OR = 0.58) (Table 4). 
Table 4
 
The Distribution of Two SNPs of ERAP1 in Patients With BD and Healthy Controls by Sex Basis
Table 4
 
The Distribution of Two SNPs of ERAP1 in Patients With BD and Healthy Controls by Sex Basis
The Expression of ERAP1
As shown above, rs1065407 and rs10050860 of ERAP1 were shown to be associated with BD. We further evaluated the expression of ERAP1 in PBMCs derived from 16 healthy individuals with a known SNP rs1065407 genotype and 16 healthy individuals with a known SNP rs10050860 genotype. The expression of ERAP1 showed no significant differences between AA carriers and AC/CC carriers of rs1065407 (P = 0.963) and CC carriers and CT/TT carriers of rs10050860 (P = 0.674) in nonstimulated PBMCs (Fig. 1). However, after stimulation by LPS, the ERAP1 expression in AA carriers was higher than that in AC or CC carriers (P = 0.022) for rs1065407, and expression in CC carriers was higher than CT or TT carriers (P = 0.018) for rs10050860 (Fig. 1). We also observed that ERAP1 mRNA levels of AA individuals and AC or CC individuals of rs1065407 were significantly increased following stimulation with LPS (P = 2.059 × 10−5; P = 0.006, respectively) when compared with nonstimulated PBMCs (Fig. 1). Similarly, ERAP1 expression of CC individuals and CT or TT individuals of rs10050860 was significantly higher when PBMCs had been stimulated with LPS as compared to nonstimulated PBMCs of CC and CT or TT carriers (P = 8.118 × 10−5; P = 7.932 × 10−5, respectively) (Fig. 1). 
Figure 1
 
Effect of genotype on ERAP1 mRNA expression of rs1065407 (A) and rs10050860 (B) by PBMCs. Peripheral blood mononuclear cells stimulated by LPS show an increased ERAP1 expression compared with nonstimulated PBMCs. Endoplasmic reticulum aminopeptidase 1 mRNA levels in AA individuals of SNP rs1065407 (A) and CC individuals of SNP rs10050860 (B) were significantly higher than AC/CC individuals and CT/TT individuals, respectively. Peripheral blood mononuclear cells were derived from healthy individuals (n = 8 per group). Data are shown as mean ± SD. **P < 0.01; *P < 0.05.
Figure 1
 
Effect of genotype on ERAP1 mRNA expression of rs1065407 (A) and rs10050860 (B) by PBMCs. Peripheral blood mononuclear cells stimulated by LPS show an increased ERAP1 expression compared with nonstimulated PBMCs. Endoplasmic reticulum aminopeptidase 1 mRNA levels in AA individuals of SNP rs1065407 (A) and CC individuals of SNP rs10050860 (B) were significantly higher than AC/CC individuals and CT/TT individuals, respectively. Peripheral blood mononuclear cells were derived from healthy individuals (n = 8 per group). Data are shown as mean ± SD. **P < 0.01; *P < 0.05.
We also measured the expression of ERAP1 in PBMCs obtained from active BD patients before they received immunosuppressive treatment (n = 9), and found that the mean expression of ERAP1 in active BD patients was significantly lower than that observed in healthy controls (P = 3.762 × 10−4) (Fig. 2). 
Figure 2
 
Endoplasmic reticulum aminopeptidase 1 expression in PBMCs derived from untreated patients with active BD (n = 9) was significantly lower than in healthy individuals (n = 16). Data are shown as mean ± SD. **P < 0.01.
Figure 2
 
Endoplasmic reticulum aminopeptidase 1 expression in PBMCs derived from untreated patients with active BD (n = 9) was significantly lower than in healthy individuals (n = 16). Data are shown as mean ± SD. **P < 0.01.
Discussion
In this study, we show an association of ERAP1 polymorphisms with BD in a Chinese Han population. Individuals carrying the AA genotype of rs1065407 and CC genotype of rs10050860 had a lower risk of developing BD. Functional assays showed that carriers of the protective variant had a higher ERAP1 expression. 
Behçet's disease is a systemic, immune-mediated vasculitis of small and large vessels affecting veins and arteries. Behçet's disease occurs worldwide, but the strongest incidence is found among people from the Middle and Far East, including Turkey, Iran, Japan, and China, countries also showing the highest frequency of HLA-B*51.3 Behçet's disease is one of the most commonly seen uveitis entities (16.5%) in China, affecting young people and often leading to visual impairment despite aggressive immunosuppressive treatment.33 Studies that may unravel the pathogenic pathways leading to this disease are therefore of utmost importance because they may offer new tools to prevent the blinding complications of this disease. 
Recent GWAS and case-control studies have revealed that naturally occurring ERAP1 polymorphisms are linked with several MHC class I–associated diseases, including AS,34,35 psoriasis,15 and BD.30,36 We undertook the study presented here in view of the fact that an association of ERAP1 with BD has not yet been reported for patients from China. Our results confirm the ERAP1 rs10050860 association with BD reported in BD patients from Turkey30 and Spain.36 Besides, the stratified analysis of ERAP1 rs10050860 association with BD by sex showed that more significant differences were found in the male population than in the female population, which suggests that ERAP1 rs10050860 may have a sex-skewed impact on BD in males. 
European studies in AS have shown that the A allele of rs1065407 and C allele of rs10050860 were reported as risk factors.21,26 The difference in risk allele of ERAP1 gene polymorphisms with AS as compared with BD is remarkable, but may be due to differences in the pathogenesis of these two disorders. In AS, peptide handling via HLA-B27 may lead to disease by a mechanism that is different from the HLA-B51–mediated peptide handling that may result in the development of BD. As mentioned above, the two SNPs influenced ERAP1 expression. When comparing genotype effects using nonstimulated PBMCs, no effects were observed. Lipopolysaccharide stimulation raised the ERAP1 expression regardless of the genotype investigated, whereby the rs1065407 AA genotype and rs10050860 CC genotype showed a higher ERAP1 expression compared with the other genotypes. We studied the effect of ERAP1 genotype on its mRNA expression in healthy controls to rule out confounding effects in patients due to the degree of inflammation and/or immunosuppressive treatment. Earlier studies demonstrated that LPS and IFN synergistically induced ERAP1 secretion from the endoplasmic reticulum in the murine macrophage cell line RAW264.7 via a Toll-like receptor–mediated signaling pathway and that the secreted ERAP1 directly enhanced the phagocytic activity of both RAW264.7 cells and murine peritoneal macrophages.37,38 These authors noted an increased expression of ERAP1 induced by LPS as well. Previous studies also found that peptide handling by ERAP1 might play a role in the pathogenesis of immune disorders such as AS.34 Cancer studies revealed that the absence or downregulated expression of ERAP1 is closely related to metastasis and invasion of lymph nodes in ovarian carcinoma.39 Others have shown that ERAP1 downregulation and partial HLA class I loss are associated with decreased survival in cervical carcinoma, with ERAP1 loss being an independent predictor for survival.40 Abrogation of endoplasmic reticulum aminopeptidase associated with antigen progressing (ERAPP) in mice induces a conformational change in the MHC class I complexes resulting in the stimulation of both innate and adaptive immune responses and the rejection of a murine lymphoma that is otherwise refractory to immune elimination.41 Knockout of the ERAAP gene elicited a CD8+ T-cell response specific for a tumor-associated antigen that is normally destroyed by ERAAP.42 These studies support the function of ERAP1 in antigen presentation and suggest that proper trimming and binding to HLA class I may play a role in the pathogenesis of BD. Moreover, we found that ERAP1 expression in healthy controls was significantly higher than BD patients, which also supports the above-mentioned hypothesis. ERAP1 SNPs may lead to alterations in ERAP1 expression and/or function, leading to decreased trimming of relevant epitopes or altered substrate specificity. Expression within the normal range and proper functioning of ERAP1 are probably necessary to maintain immune tolerance. 
There are a number of limitations in our study that we would like to mention. Although we tried to match the controls for sex, 84% of cases were male whereas only 56% of controls were male. The association found is small because 91% of healthy Chinese are rs1065407 AA carriers as compared with 83% of the BD patients. Similar differences are found for rs10050860 CC (92% in controls versus 86% in BD). Of interest is the observation that the genotype frequency of rs10050860 CC is much lower in a European population (62%) as compared with Chinese Han (92%).21 The association of ERAP1 with BD is only one factor among many immune response–related genes that are now emerging to play a role in BD.43 Further research is needed to elucidate the relative contributions of each of them. It is known that BD is a systemic disease and that the patients recruited from an ophthalmology department may represent a subpopulation of this disease. Therefore, the susceptible SNPs identified in our study may only be associated with uveitis in BD and it is therefore necessary to expand our studies and also investigate the association of ERAP1 with BD in Han Chinese patients from other medical departments. We showed that active BD patients had a lower ERAP1 expression compared with controls but further longitudinal studies are needed to examine the effect of treatment and disease activity on ERAP1 expression during the course of the disease. Given that the examination of HLA-B51 was not performed in all BD patients and healthy controls, we did not assess the role of HLA-B51 in our study and did not investigate whether there is an interaction with ERAP1 polymorphisms and HLA-B51. This deserves further study and would support the role of ERAP1 in the presentation of antigens via HLA-B51. In conclusion, our study showed that rs1065407 and rs10050860 polymorphisms in the ERAP1 gene contribute to the genetic susceptibility of BD. In addition, our study suggested that the gene variants identified may affect the genetic predisposition by modulating the expression of ERAP1
Acknowledgments
The authors thank the patients and controls for their participation in this study. 
Supported by Natural Science Foundation Major International (Regional) Joint Research Project (81320108009), Key Project of Natural Science Foundation (81130019), National Natural Science Foundation Project (31370893, 81200678), Research Fund for the Doctoral Program of Higher Education of China (20115503110002), Basic Research Program of Chongqing (cstc2013jcyjC10001), Chongqing Key Laboratory of Ophthalmology (CSTC, 2008CA5003), National Key Clinical Specialties Construction Program of China, Key Project of Health Bureau of Chongqing (2012-1-003), Research fund for Traditional Chinese Medicine of Chongqing Health and Family Planning Commission (ZY201401013), Chongqing Science and Technology Platform and Base Construction Program (cstc2014pt-sy10002) and Fund for PAR-EU Scholars Program. The authors alone are responsible for the content and the writing of the paper. 
Disclosure: L. Zhang, None; H. Yu, None; M. Zheng, None; H. Li, None; Y. Liu, None; A. Kijlstra, None; P. Yang, None 
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Figure 1
 
Effect of genotype on ERAP1 mRNA expression of rs1065407 (A) and rs10050860 (B) by PBMCs. Peripheral blood mononuclear cells stimulated by LPS show an increased ERAP1 expression compared with nonstimulated PBMCs. Endoplasmic reticulum aminopeptidase 1 mRNA levels in AA individuals of SNP rs1065407 (A) and CC individuals of SNP rs10050860 (B) were significantly higher than AC/CC individuals and CT/TT individuals, respectively. Peripheral blood mononuclear cells were derived from healthy individuals (n = 8 per group). Data are shown as mean ± SD. **P < 0.01; *P < 0.05.
Figure 1
 
Effect of genotype on ERAP1 mRNA expression of rs1065407 (A) and rs10050860 (B) by PBMCs. Peripheral blood mononuclear cells stimulated by LPS show an increased ERAP1 expression compared with nonstimulated PBMCs. Endoplasmic reticulum aminopeptidase 1 mRNA levels in AA individuals of SNP rs1065407 (A) and CC individuals of SNP rs10050860 (B) were significantly higher than AC/CC individuals and CT/TT individuals, respectively. Peripheral blood mononuclear cells were derived from healthy individuals (n = 8 per group). Data are shown as mean ± SD. **P < 0.01; *P < 0.05.
Figure 2
 
Endoplasmic reticulum aminopeptidase 1 expression in PBMCs derived from untreated patients with active BD (n = 9) was significantly lower than in healthy individuals (n = 16). Data are shown as mean ± SD. **P < 0.01.
Figure 2
 
Endoplasmic reticulum aminopeptidase 1 expression in PBMCs derived from untreated patients with active BD (n = 9) was significantly lower than in healthy individuals (n = 16). Data are shown as mean ± SD. **P < 0.01.
Table 1
 
Primers and Restriction Enzymes Used for RFLP Analysis
Table 1
 
Primers and Restriction Enzymes Used for RFLP Analysis
Table 2
 
Clinical Characteristics, Sex, and Age of BD Patients With Uveitis
Table 2
 
Clinical Characteristics, Sex, and Age of BD Patients With Uveitis
Table 3
 
Association of Two SNPs of ERAP1 With BD
Table 3
 
Association of Two SNPs of ERAP1 With BD
Table 4
 
The Distribution of Two SNPs of ERAP1 in Patients With BD and Healthy Controls by Sex Basis
Table 4
 
The Distribution of Two SNPs of ERAP1 in Patients With BD and Healthy Controls by Sex Basis
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